1. Field of the Invention
The present invention relates to wire communications. More particularly, the present invention relates to telephone twisted pair copper wire communications using loaded cables.
2. Background Information The existing methods for transmitting data communication over loaded (conditioned) twisted pair copper wire use various modulation techniques that manipulate a carrier(s) by phase, amplitude and/or frequency, and uses voltage detection. FIG. 1 illustrates a diagram of the conventional modulation techniques used in today""s transmission technology.
Referring to FIG. 1, data 10 includes information that may be transmitted over the loaded twisted pair using one of the illustrated transmission techniques. Data 10 is represented by digital signals that are transmitted in strings of binary 1s and 0s. When amplitude modulation technique 20 is used to transmit data 10, the data signal is blended into a carrier by varying the amplitude of the carrier. Specifically, the amplitude is modulated when it corresponds to a binary 0 of the data signal. On-off modulation technique 30 uses a transmitter which is turned off every time the transmitted data signal is represented by a binary 0. When frequency modulation using frequency shift keying (FSK) technique 40 is used, the data signal is blended into a carrier by modulating (shifting) the frequency of the carrier. The frequency shift occurs when a binary 0 in the data signal is encountered. Phase modulation using phase shift keying (PSK) technique 50 shifts the phase (e.g., 180xc2x0) when the data signal represented by a binary 0 is transmitted. Using various modulation techniques, the twisted pair communication industry has obtained data rates of up to 56 kilobits at 50,000 feet over loaded cabled facilities. Some of these systems use multiple carrier frequency such as DSS (Digital Spread Spectrum), DMT (Digital Multi-Tone), OFDM (Orthogonal Frequency Division Multiplexing) and others. The use of these signaling techniques is limited by the load coils flattening of voltages of frequencies above 3300 hertz in the voltage domain.
The object of the present invention is to provide a loaded cable twisted pair communications transmission system that can transmit information at high rates with high QoS (Quality of Service). By using a differential voltage transmitting an offset low frequency sinusoidal signal within the voice spectrum, that uses an on-off keying (OOK) modulator at the rate of the data being transmitted, high bandwidth transmission speeds can be achieved. In one embodiment, the On/Off state of the low frequency sinusoidal signal can be coupled using state of the art techniques used in the digital subscriber line (DSL) field. Using various coupling techniques, the transmitted information may be used in conjunction with existing analog telephone service and plain old telephone service (POTS) being provided on the loaded twisted pair copper wire by filtering the specific sinusoidal signal frequency out of the circuit.
One of the advantages of the present invention is that the signal transmitted is a transverse electromagnetic (T.E.M.) wave with an ultra-wide bandwidth. When using this transmission technique for video, voice and data communications, the invention may enable the QoS, reliability and bit error rate required for each service provided.
To provide telephone (voice) services to, from and within the home or office the telephone must work for emergency services when power is out. The present invention may provide the ability to not only transmit and receive high-speed information, but to also provide telephone emergency service in any state that the home or office electrical service is in.
In one embodiment, information is transmitted over loaded twisted pairs using the telephone utility outside plant copper wiring. By modulating a low sinusoidal signal frequency (within the voice frequency range), offset signal, using OOK differentially, high speed transmissions (e.g., speeds of 52 megabits per second) may be provided over the existing conditioned twisted pair infrastructure using current detection techniques. When load coils are in the outside plant, they do not modify the current. However, they do attenuate the voltage (current in is equal to current out). The differential nature of the TEM transmission is maintained through numerous load coils and the signal is attenuated according to the gage and distance of the wire involved.
Another object of the present invention is to provide cable television-type service capabilities over the loaded twisted pair wires. If a TV is equipped with the present invention, or a set-to-box is connected, digital TV signals may be sent from a source over the loaded twisted pair copper wires to the television receiver over extended distances (e.g., distances of over 50,000 feet from the transmitter).
Another object of the present invention is to transmit high volumes of voice transmissions (telephone conversations) over loaded twisted pairs and interconnect this transmission to the existing public telephone network system.
Another object is to use the loaded twisted pair transmission technology to interface into the other transmission equipment environments, such as, for example, providing trunking or concentrating communication traffic from wireless devices, or LAN (local area network) to a centralized location or peer-to-peer connections.
Another object of the invention is the ability for this technology to be channelized to provide isochronous, asynchronous, synchronous, and bi-synchronous transmissions. Video and voice could be isochronous and high-speed data transfers between computers would be asynchronous. In one embodiment, all information is sent serially.
Another object of the invention is the ability for video, voice and data to be intermixed in the twisted pair communication system. This may allow to distribute various applications (e.g., satellite, radio, cellular, microwave, PCS, telephone, audio, Internet and television communication, transmission and reception) over the loaded twisted pair copper wiring.
In one embodiment, the present invention provides differential voltage, offset frequency, OOK as a transmission technology using a base sinusoidal wave (e.g., a base sinusoidal waive between 400 to 3,300 hertz). By adjusting the base sinusoidal wave to the best power spectrum, better signal to noise ratio can be achieved. This sinusoidal wave is OOK to the ON position when a binary 1 (one) is sent from a digital data source and turned to the OFF position when a 0 (zero) is present, however, this configuration may be inverted. Using conventional encoding and decoding schemes known in the industry, all control and timing information may be transmitted within the serial bit stream provided in the transmission technique. In one embodiment, the information/data from a digital source (e.g., PC, computer, audio system, VCR, etc.) may be transmitted into a buffer and then sent to an OOK modulator. The modulator controls the ON and OFF states of the base sinusoidal wave transmission. Each ON state of the base sinusoidal wave transmitted may then be sent as a forward biased low frequency sine wave with enough current to drive the circuit for the duration of the ON symbol. Further, the signal may be sent into a coupler to be connected to the loaded twisted pair copper wire infrastructure. The transmitted signal may then be received at the far end and decoupled using a filter device. In one embodiment, the signal is received having a resistive load and input into an optocoupler device to convert and isolate the circuit. The receiver is current sensing and converts current to voltage. Once the current has been converted to voltage, the voltage may be sent to a differential Op Amp circuit to amplify the signal. In one embodiment, a low voltage differential signal receiver converts the wave form into a square wave that the receiving communication device can convert into a binary 1 (one) or binary 0 (zero) logic state. The transmission may be detected as a differential current event using the transmission initial conditions. By using a differential signal method and the T.E.M. waveform, the effect of standard noise conditions found in the twisted pair on the transmission is reduced. By providing a differential base voltage, the noise floor on the transmission is raised and the transmission has an improvement on the SNR (signal-to-noise ratio). In one embodiment, the low frequencies sinusoidal wave used in the transmitter may be generated by voltage-controlled oscillators.